Those of a nervous disposition when it comes to flying will not have enjoyed the news that France's freshly inaugurated president was forced to return to Paris mid-flight on Tuesday when his jet was struck by lightning. It was probably not the omen François Hollande was seeking as he travelled to Berlin for his first meeting with Angela Merkel.

But lightning strikes are not something passengers need necessarily concern themselves with, according to Professor Manu Haddad, who works at Cardiff University's recently opened "lightning lab" – or, to use its more formal name, the School of Engineering's Morgan Botti Laboratory. "On average, every commercial aircraft is hit by lightning once a year," says Haddad, whose lab specialises in testing how to protect aircraft from lightning. "It is routine for an aircraft to land as soon as possible after a strike, but this is a precautionary measure. Lightning is extremely hot – up to 30,000C. The typical damage is a scorch mark where the point of contact was, usually a wing-tip. The plane's electronics are well shielded these days."

Haddad says strikes normally occur soon after take-off when the plane is still beneath the storm clouds, which are 2-5km in altitude. "I don't know of a modern-era example where a lightning strike alone has brought down a plane," he says. "It's the same principle as being protected in a car. A metal box such as a car or plane is known as a Faraday cage, which protects those inside from the current. Planes are now built to absorb 250,000 amps, whereas the average strike generates 32,000 amps.

"It only gets really serious when the radome [nose cone] is struck, the only part of the plane's shell not made of metal, as this is where the radar is located. But nose cones have special lightning conductors for just this reason."

And what of the passengers inside? "They usually won't notice a thing, or they might just see a bright flash."